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US 2018/0000523 A1Published application
Polyaxial bone screw with shank articulation pressure insert and method
OwnerRoger P. Jacksoninventor
Life of this patent
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Abstract
A polyaxial bone screw assembly includes a threaded shank body having an upper portion, a receiver member or head, a retaining and articulating structure, and a pressure insert disposed between the shank upper portion and a rod. The receiver has a U-shaped cradle defining a channel for receiving a spinal fixation rod and a receiver cavity. The retaining and articulating structure attaches to the shank and rotates with the shank in the cavity during positioning. The pressure insert presses upon the shank upper portion and not the retaining and articulating structure.
Claims38
A pivotal bone anchor assembly for securing an elongate rod to a bone, the pivotal bone anchor assembly comprising:
- a receiver having a longitudinal axis, a first pair of opposed upstanding arms extending upwardly from a lower body to define an upwardly open channel configured to receive the elongate rod, and a cavity within the lower body communicating with the open channel and with a downward facing bottom surface of the receiver through a distal opening in the lower body, the cavity having a substantially spherical inner seating surface adjacent to the distal opening, the upstanding arms having spaced apart and opposed interior surfaces with a discontinuous guide and advancement structure formed into upper portions thereof, and a pair of opposed upper recesses and at least one pair of opposed lower insert engaging recesses formed therein between the guide and advancement structure and the cavity, the upper and lower opposed recesses separated by opposed inwardly facing interior edges having a width less than a width for both the upper and lower opposed recesses;
- a bone anchor disposed within the receiver, the bone anchor having a proximal end portion and an anchor portion extending distally from the proximal end portion and through the distal opening for fixation to the bone, the proximal end portion having a partial spherically shaped outer upper surface above a hemisphere thereof;
- and
- a pressure insert positioned within the receiver channel above the bone anchor partial spherically shaped outer upper surface, the pressure insert comprising a base with a second pair of opposed upstanding arms extending upward from the base to define a curvate rod-engaging seating surface therebetween, the second pair of opposed upstanding arms having laterally facing outer surfaces extending down to the base to define substantially continuous lateral side surfaces devoid of any inwardly extending groove, aperture or slot, each of the lateral side surfaces having an upper section with a receiver engagement structure protruding laterally outward and extending upward to an upwardly-facing top surface thereon,
- wherein the pressure insert is directly engageable and downwardly displaceable using a removable first tool within the receiver channel after the bone anchor proximal end portion is disposed within the receiver cavity to apply pressure to the bone anchor upper surface, with the top surface of the laterally protruding receiver engagement structure being received in biased and at least partially overlapped engagement with a downwardly-facing top surface on the at least one pair of opposed lower insert engage recesses so as to prevent the insert from moving upwardly thereafter within the receiver prior to insertion of the elongate rod and a closure into the receiver channel.
2 more elements
A bone anchor assembly for securing an elongate rod to a bone, the bone anchor assembly comprising:
- a shank having a proximal capture portion with a top surface and an anchor portion extending distally from the proximal capture portion for fixation to the bone;
- a receiver having a longitudinal axis, an upper portion defining a upwardly open channel with inner sidewall surfaces configured to receive the elongate rod, and a lower portion defining a cavity having an interior surface communicating with the open channel and a receiver bottom opening, the shank positionable within the receiver with the shank anchor portion extending through the bottom opening, the inner sidewall surfaces including a closure mating structure formed therein, the receiver having an internal structure with a downwardly-facing surface located between the closure mating structure and the receiver bottom opening;
- a closure positionable within the receiver open channel;
- and
- a pressure insert sized and shaped to be initially disposed adjacent the receiver internal structure downwardly-facing surface and engaged by a tool so as to be downwardly displaceable within the receiver, after the shank has been positioned within the receiver cavity, the pressure insert having an outer surface configured to engage the receiver internal structure downwardly-facing surface in an overlapping relationship, the receiver internal structure downwardly-facing surface being formed in the receiver before the pressure insert is disposed within the receiver open channel,
- wherein the insert outer surface and the receiver internal structure downwardly-facing surface have a frictionally-biased overlapping engagement therebetween to frictionally hold and prevent the insert from moving back up within the receiver prior to the elongate rod and the closure being received within the receiver open channel, and
- wherein when the bone anchor assembly is in a locked position, with the elongate rod and closure within the receiver open channel, the closure remains spaced from the pressure insert.
4 more elements
A pivotal bone anchor assembly for securing an elongate rod to a bone, the pivotal bone anchor assembly comprising:
- a closure;
- a receiver defining an internal cavity in communication with an upper open channel and with a bottom surface of the receiver through a lower opening, the open channel being configured to receive the elongate rod and the closure above the elongate rod to secure the elongate rod to the receiver;
- a shank having an upper portion and a body for fixation to the bone, the upper portion being pivotably positioned within a lower portion of the receiver internal cavity with the shank body extending downward through the lower opening;
- and
- a pressure insert at least partially positionable within the open channel and operably engageable by a tool after the shank is disposed within the internal cavity to move an outer engagement surface of the pressure insert into at least partially overlapped contact with a receiver internal structure mating surface formed in the receiver before the insert is positioned therein, so as to bias the shank upper portion into a frictional articulatable relationship with the receiver prior to the assembly being locked with the closure and to prevent the insert from moving back up within the upper open channel,
- wherein the pressure insert is spaced from the closure when the closure and rod are positioned within the open channel.
3 more elements
Dependencies are inferred from the claim text.